pH-sensitive green tea-derived carbon quantum dots for real-time monitoring of shrimp freshness

Green-emitting carbon dots (CDs) were synthesized via a one-step hydrothermal approach using green tea leaf powder (GLP) as a single precursor. The stability and effectiveness of the synthesized GLP-CDs were verified by zeta potential, optical, and luminescence analyses. The prepared CD has excellent pH-responsive properties, providing exciting possibilities for pH-induced intelligent monitoring of packaged foods. GLP-CD was useful for determining liquid ammonia in the linear range of 1–100 μM with the lowest detection limit of 0.4 μM. Additionally, the paper indicator coated with GLP-CDs exhibits a sharp color change from yellow to brown, indicating its ability to detect ammonia vapor. The efficacy of the GLP-CDs-based paper indicator was evaluated as a real-time freshness indicator of shrimp packaging by determining total volatile basic nitrogen. The paper indicator based on GLP-CD has proven to be a simple and cost-effective system for visually monitoring shrimp freshness in the field for suppliers and consumers.